chore(doc): Replace Chinese comments with English comments

frontend/Dockerfile

@@ -1,4 +1,4 @@
-# 多阶段构建 - 构建阶段
+# Multi-stage build — build stage
 FROM node:18-alpine AS builder
 
 ARG HTTP_PROXY
@@ -10,54 +10,54 @@ ENV http_proxy ${HTTP_PROXY} \
     no_proxy ${NO_PROXY}
 
 WORKDIR /app
-# 复制package文件
+# Copy package files
 COPY package*.json ./
 COPY pnpm-lock.yaml ./
 
-# 安装pnpm（使用npm，避免网络问题）
+# Install pnpm
 RUN npm install -g pnpm --no-audit --no-fund
 
-# 安装依赖
+# Install dependencies
 RUN pnpm install --frozen-lockfile
 
-# 复制源代码
+# Copy source code
 COPY . .
 
-# 在依赖安装之后再声明与使用构建期公开变量，避免仅 API/TURN 改动导致依赖层缓存失效
+# Declare and use build-time public vars after deps installation to avoid cache invalidation when only API/TURN change
 ARG NEXT_PUBLIC_API_URL
 ARG NEXT_PUBLIC_TURN_HOST
 ARG NEXT_PUBLIC_TURN_USERNAME
 ARG NEXT_PUBLIC_TURN_PASSWORD
 
-# 前端构建期注入可公开环境变量（用于客户端直连后端与 TURN）
+# Inject public env vars during frontend build (for client direct access to backend and TURN)
 ENV NEXT_PUBLIC_API_URL=${NEXT_PUBLIC_API_URL}
 ENV NEXT_PUBLIC_TURN_HOST=${NEXT_PUBLIC_TURN_HOST}
 ENV NEXT_PUBLIC_TURN_USERNAME=${NEXT_PUBLIC_TURN_USERNAME}
 ENV NEXT_PUBLIC_TURN_PASSWORD=${NEXT_PUBLIC_TURN_PASSWORD}
 
-# 设置环境变量
+# Set environment variables
 ENV NEXT_TELEMETRY_DISABLED 1
 ENV NODE_ENV production
 
-# 构建应用
+# Build the app
 RUN pnpm build
 
-# 生产阶段
+# Production stage
 FROM node:18-alpine AS runner
 
 WORKDIR /app
 
-# 创建非root用户
+# Create a non-root user
 RUN addgroup -g 1001 -S nodejs && \
     adduser -S nextjs -u 1001 -G nodejs
 
-# 复制构建产物
+# Copy build artifacts
 COPY --from=builder /app/public ./public
 COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
 COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
 COPY health-check.js ./
 
-# 设置环境变量
+# Set environment variables
 ENV NODE_ENV production
 ENV NEXT_TELEMETRY_DISABLED 1
 ENV PORT 3002
@@ -65,18 +65,18 @@ ENV HOSTNAME "0.0.0.0"
 
 USER nextjs
 
-# 暴露端口
+# Expose ports
 EXPOSE 3002
 
-# 使用Node.js脚本做健康检查（替代curl）
+# Use a Node.js script for health checks (instead of curl)
 HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
   CMD node health-check.js
 
-# 启动应用
+# Start the app
 CMD ["node", "server.js"]
 
-# 运行期保留公开变量（非必需，但便于服务端渲染读取）
-# 需在当前阶段重新声明 ARG，以便在此阶段展开到 ENV
+# Keep public env vars at runtime (optional; helps SSR read them)
+# Re-declare ARGs in this stage so they can expand into ENV
 ARG NEXT_PUBLIC_API_URL
 ARG NEXT_PUBLIC_TURN_HOST
 ARG NEXT_PUBLIC_TURN_USERNAME